CI_Migration::__construct PHP Method

    public function __construct($config = array())
    {
        // Only run this constructor on main library load
        if (!in_array(get_class($this), array('CI_Migration', config_item('subclass_prefix') . 'Migration'), TRUE)) {
            return;
        }
        foreach ($config as $key => $val) {
            $this->{'_' . $key} = $val;
        }
        log_message('info', 'Migrations Class Initialized');
        // Are they trying to use migrations while it is disabled?
        if ($this->_migration_enabled !== TRUE) {
            show_error('Migrations has been loaded but is disabled or set up incorrectly.');
        }
        // If not set, set it
        $this->_migration_path !== '' or $this->_migration_path = APPPATH . 'migrations/';
        // Add trailing slash if not set
        $this->_migration_path = rtrim($this->_migration_path, '/') . '/';
        // Load migration language
        $this->lang->load('migration');
        // They'll probably be using dbforge
        $this->load->dbforge();
        // Make sure the migration table name was set.
        if (empty($this->_migration_table)) {
            show_error('Migrations configuration file (migration.php) must have "migration_table" set.');
        }
        // Migration basename regex
        $this->_migration_regex = $this->_migration_type === 'timestamp' ? '/^\\d{14}_(\\w+)$/' : '/^\\d{3}_(\\w+)$/';
        // Make sure a valid migration numbering type was set.
        if (!in_array($this->_migration_type, array('sequential', 'timestamp'))) {
            show_error('An invalid migration numbering type was specified: ' . $this->_migration_type);
        }
        // If the migrations table is missing, make it
        if (!$this->db->table_exists($this->_migration_table)) {
            $this->dbforge->add_field(array('version' => array('type' => 'BIGINT', 'constraint' => 20)));
            $this->dbforge->create_table($this->_migration_table, TRUE);
            $this->db->insert($this->_migration_table, array('version' => 0));
        }
        // Do we auto migrate to the latest migration?
        if ($this->_migration_auto_latest === TRUE && !$this->latest()) {
            show_error($this->error_string());
        }
    }

 public function __construct($config = array())
 {
     parent::__construct();
     // Loading the configuration fo migration
     $this->config->load('migration');
     foreach ($this->config->config as $key => $val) {
         $this->{'_' . $key} = $val;
     }
     log_message('debug', 'Migrations class initialized');
     // Are they trying to use migrations while it is disabled?
     if ($this->_migration_enabled !== TRUE) {
         show_error('Migrations has been loaded but is disabled or set up incorrectly.');
     }
     // If not set, set it
     $this->_migration_path == '' and $this->_migration_path = APPPATH . 'migrations/';
     // Add trailing slash if not set
     $this->_migration_path = rtrim($this->_migration_path, '/') . '/';
     // Load migration language
     $this->lang->load('migration');
     // They'll probably be using dbforge
     $this->load->dbforge();
     // If the migrations table is missing, make it
     if (!$this->db->table_exists('migrations')) {
         $this->dbforge->add_field(array('version' => array('type' => 'INT', 'constraint' => 3)));
         $this->dbforge->create_table('migrations', TRUE);
         $this->db->insert('migrations', array('version' => 0));
     }
 }